The prior art includes U.S. Pat. No. 3,990,195 issued to R. R. Gunther on November 9, 1976 for "HUB FOR GEODESIC DOME FRAMEWORK CONSTRUCTION". That patent discloses a spider-like connector construction of plates forming at least three single arms radially deployed from a hub comprising a central metal rod. Each plate has a slot and a hole or else two holes passing through it to receive fasteners for holding an end of a respective strut which is slotted to slip over the plate and which has holes matching the opening in the plate.
The aforesaid U.S. Pat. No. 3,990,195 stresses the need for at least two openings in each plate and apart from the fasteners provides no means of limiting travel of the struts under load radially toward the center to prevent further splitting of the struts by the plates if the fasteners are loose or in oversize holes. Further, there appears to be little or no provision for minimizing bending loads on the plates in circumferential direction. Still further, the weld at the center which holds the 3/8 inch diameter rod to the plates appears to be necessarily made in cramped quarters where cracks would be difficult to see and where all parts of the central junction might have to be heated as many times as there are arms, opening the way for expansion and contraction cracking. If cast instead of welded, the central junction presents difficulties of inspection and the same small-scale difficulties in welded or in cast construction tend to produce stress concentration in any case.
Further, the small solid central junction makes coverage of the central portion difficult to inspect from inside the dome.
U.S. Pat. No. 4,122,646 issued to D. H. Sapp on 10-31-78 discloses an elongate finned tube derrick connector having a circular tube with single fins or arms radiating from it but with ends perpendicular to long axis.